Abstract- [18F]UCB-H is a novel radiotracer with a high affinity for SV2A, a protein expressed in synaptic vesicles. SV2A is the binding site of levetiracetam, a “first in class” antiepileptic drug with a ... [more ▼]

Abstract- [18F]UCB-H is a novel radiotracer with a high affinity for SV2A, a protein expressed in synaptic vesicles. SV2A is the binding site of levetiracetam, a “first in class” antiepileptic drug with a distinct but still poorly understood mechanism of action. The objective of this study was to determine the biodistribution and radiation dosimetry of [18F]UCB-H in a human clinical trial and to establish injection limits according to biomedical research guidelines. Additionally, the clinical radiation dosimetry results were compared to estimations in previously published preclinical data. Dynamic whole body PET/CT imaging was performed over approximately 110 minutes on five healthy male volunteers after injection of 144.5 ± 7.1 MBq (range, 139.1 – 156.5 MBq) of [18F]UCB-H. Major organs were delineated on CT images and time-activity curves were obtained from co-registered dynamic PET emission scans. Time-integrated activity coefficients were calculated as area under the curve using trapezoidal numerical integration. Urinary excretion data based on PET-activities including voiding was simulated using the dynamic bladder module of OLINDA/EXM. The radiation dosimetry was calculated using OLINDA/EXM. The effective dose to the OLINDA/EXM 70 kg standard male was 1.54E-02 ± 6.84E-04 mSv/MBq, with urinary bladder wall, gallbladder wall and the liver receiving the highest absorbed dose. The brain, the tracer’s main organ of interest, received an absorbed dose of 1.89E-02 ± 2.32E-03 mGy/MBq. This first human dosimetry study of [18F]UCB-H indicated that the tracer shows similar radiation burdens to widely used common clinical tracers. Single injections of at maximum 672 MBq for USA practice and 649 MBq for European practice keep radiation exposure below recommended limits. Recently published preclinical dosimetry data extrapolated from mice provided satisfactory prediction of total body and effective dose, but showed significant differences in organ absorbed doses compared to human data. [less ▲]

SV2A is widely distributed in the brain and has been demonstrated to be involved in vesicle trafficking. The critical role of SV2A in proper nervous system function is shown, e.g., by the fact that it is ... [more ▼]

SV2A is widely distributed in the brain and has been demonstrated to be involved in vesicle trafficking. The critical role of SV2A in proper nervous system function is shown, e.g., by the fact that it is a binding site and the primary mechanism of levetiracetam. Levetiracetam is an antiepileptic drug which has recently been suggested to reduce synaptic deficits in a mouse model for Alzheimer’s disease. We here aimed to investigate the cerebral distribution of [18F]UCB-H, which has a high affinity with the SV2A. Dynamic PET data of the head of 4 healthy volunteers were acquired over 100 minutes after injection of 170.4 ± 24.9 MBq of GMP produced [18F]UCB-H. The arterial input function (IF) was obtained by blood sampling. The IF was also derived from the dynamic data using the correlation coefficient method. Blood data revealed a consistent amount of [18F]UCB-H in whole blood and plasma indicating a very low degree of binding of the tracer to the red blood cells. The image-derived arterial IFs were showed to be very similar to the measured ones with a peak-ratio around 0.91 and an area-under-curve ratio about 0.98. The [18F]UCB-H PET data showed a high and rapid uptake in the grey matter structures, matching the known ubiquitous distribution of the SV2A in the brain. The kinetics of the tracer in the brain was characterized by an initial high uptake phase followed by rapid washout allowing the standard compartmental modeling (1-tissue, 2-tissue, and Logan Plot). The three models gave similar results with both the measured and image-derived IFs. The total distribution volume of the tracer in the brain was greater than 7 mL/cm3. Our results suggest that [18F]UCB-H is a good candidate as radiotracer for brain SV2A proteins and could be used for human studies. Image-derived IF showed to be useful for quantitative studies without the need to the arterial blood sampling. SV2A modifications may consequently be assessed in neurological pathologies such as Alzheimer’s disease. [less ▲]

ABSTRACT: Indoleamine 2,3-dioxygenase (hIDO) is an enzyme that catalyzes the oxidative cleavage of the indole ring of L-tryptophan through the kynurenine pathway, thereby exerting immunosuppressive ... [more ▼]

ABSTRACT: Indoleamine 2,3-dioxygenase (hIDO) is an enzyme that catalyzes the oxidative cleavage of the indole ring of L-tryptophan through the kynurenine pathway, thereby exerting immunosuppressive properties in inflammatory and tumoral tissues. The syntheses of 1-(2-fluoroethyl)-tryptophan (1-FETrp) and 1-((1-(2-fluoroethyl)-1H-1,2,3-triazol-4-yl)methyl)-tryptophan, two N1-fluoroalkylated tryptophan derivatives, are described here. In vitro enzymatic assays with these two new potential substrates of hIDO show that 1-FETrp is a good and specific substrate of hIDO. Therefore, its radioactive isotopomer, 1-[18F]FETrp, should be a molecule of choice to visualize tumoral and inflammatory tissues and/or to validate new potential inhibitors. [less ▲]

Synaptic vesicle 2 (SV2) proteins are critical to proper nervous system function and are involved in vesicle trafficking. The SV2A isoform has been identified as the binding site of the antiepileptic ... [more ▼]

Synaptic vesicle 2 (SV2) proteins are critical to proper nervous system function and are involved in vesicle trafficking. The SV2A isoform has been identified as the binding site of the antiepileptic levetiracetam (LEV), making it an interesting therapeutic target for epilepsy. [18F]UCB-H is a novel PET imaging agent with a nanomolar affinity for human SV2A. Methods: preclinical PET studies were carried out in isoflurane anesthetized rats. Arterial input function was measured using an arteriovenous shunt and beta microprobe system. [18F]UCB-H was injected IV (140 ± 20 MBq bolus). Results: brain uptake of [18F]UCB-H was high, matching the expected homogeneous distribution of SV2A. The distribution volume (Vt) for [18F]UCB-H was calculated using Logan’s graphical analysis and the effect of LEV pretreatment on Vt measured. In control animals the mean whole-brain Vt was 9.76 ± 0.52 ml/cm3 (mean ± SD, n=4, test-retest), and the mean reproducibility in test-retest studies was 10.4 ± 6.5 %. Uptake of [18F]UCB-H was dose-dependently blocked by pretreatment with LEV (0.1 - 100 mg/kg IV). Conclusion: our results indicate that [18F]UCB-H is a suitable radiotracer for the imaging of SV2A in vivo. This is the first PET tracer for in vivo quantification of SV2A. The necessary steps for implementation of [18F]UCB-H production under GMP conditions and first in human studies are planned. [less ▲]

Synaptic vesicle protein 2A (SV2A) is widely distributed in the brain and has been demonstrated to be involved in vesicle trafficking. The critical role of SV2A in proper nervous system function is shown ... [more ▼]

Synaptic vesicle protein 2A (SV2A) is widely distributed in the brain and has been demonstrated to be involved in vesicle trafficking. The critical role of SV2A in proper nervous system function is shown, for example, by the fact that it is a binding site and the primary mechanism of levetiracetam. Levetiracetam is an antiepileptic drug which has recently been suggested to reduce synaptic deficits in a mouse model for Alzheimer’s disease and to improve cognition in patients with amnestic mild cognitive impairment. We here aimed to investigate the cerebral distribution of [18F]UCB-H, a fluorine-18 radiolabelled PET imaging tracer, which has a high affinity with the SV2A. [18F]UCB-H was radiosynthesized under GMP conditions. Dynamic PET data of the head of four healthy volunteers were acquired over 100 minutes after injection of 170.4 ± 24.9 MBq of [18F]UCB-H. The arterial input function was obtained by blood sampling during the dynamic PET acquisition. The analysis of the blood data reveled a consistent amount of [18F]UCB-H in whole blood and plasma which indicates a very low degree of binding of the tracer to the red blood cells. The unchanged fraction of [18F]UCB-H in plasma showed a bi-exponential behavioral decrease with a starting fraction of 92% of the injected amount of the tracer, measured at 3 min post injection. This fraction decreased to about 50% at 10 min post injection. The [18F]UCB-H PET data showed a high and rapid uptake in the grey matter structures, matching the known ubiquitous distribution of the SV2A in the brain. The kinetics of the tracer in the brain was characterized by an initial high uptake phase followed by rapid washout allowing the standard compartmental modeling (1-tissue compartment, 2-tissue compartment, and Logan graphical analysis). The three models gave consistent results. The two-tissue compartment model fitted the experimental data best and provided a total distribution volume of the [18F]UCB-H in the brain greater than 7 mL/cm3 and a specific distribution volume around 3 mL/cm3. Our results suggest that [18F]UCB-H is a good candidate as radiotracer for brain SV2A proteins and could be used for human studies. In the future, SV2A modifications might be assessed in neurological pathologies such as Alzheimer’s disease. [less ▲]

The AMPA subtype of glutamatergic receptors is the main actor in the excitatory neurotransmission in the mammalian central nervous system. These receptors are involved in the expression and the ... [more ▼]

The AMPA subtype of glutamatergic receptors is the main actor in the excitatory neurotransmission in the mammalian central nervous system. These receptors are involved in the expression and the maintenance of the long-term potentiation, a phenomenon closely linked to cognitive and memorization processes. Based on experimental data collected in recent years, the use of AMPA potentiators seems to be an interesting approach in the treatment of cognitive deficits (e.g. Alzheimer disease), schizophrenia or depression. Such AMPA signal potentiation could be mediated by positive allosteric modulators (PAMs) of the AMPA receptors, a class of compounds able to produce a fine signal tuning in the presence of the endogenous ligand in the synapse, providing less toxicity than direct agonists. With this approach, the laboratory of Medicinal Chemistry of Liège university developed many series of AMPA potentiators , among which 1,2,4-benzothiadiazine 1,1-dioxides (BTDs). In order to better understand the in vivo mapping of AMPA receptors and its evolution in neurological diseases, the present work aims at developing the design and the synthesis of BTDs positive allosteric modulators radiolabeled with a fluorine-18 atom. Based on previously synthesized series in this field, we investigate the synthesis of a new class of high-affinity AMPA potentiators characterized by the presence of a fluorine atom at selected positions on the structure of the AMPA potentiators. Thanks to in vitro pharmacological evaluations, we will further determine the best candidates for their fluorine-18 radiolabeling. [less ▲]

Indoleamine 2,3-dioxygenase (rhIDO) is an enzyme mainly expressed in brain and tumor cells and catalyzing the oxidative cleavage of the indole ring of L-tryptophan through the kynurenine pathway ... [more ▼]

Indoleamine 2,3-dioxygenase (rhIDO) is an enzyme mainly expressed in brain and tumor cells and catalyzing the oxidative cleavage of the indole ring of L-tryptophan through the kynurenine pathway. Furthermore this enzyme could be responsible for the eventual suppression of immune responses by blocking locally T-lymphocyte proliferation. The syntheses of 1-(2-fluoroethyl)-tryptophan (1-[19F]FETrp) and 1-((1-(2-fluoroethyl)-1H-1,2,3-triazol-4-yl)methyl)-tryptophan, two N-fluoroalkylated tryptophan derivatives, are described here. In vitro enzymatic assays with these two new potential substrates of rhIDO show that 1-[19F]FETrp is a good and specific substrate of hIDO. [less ▲]

The mammalian proteins, Nod1 and Nod2, are able to recognize peptidoglycan motifs during bacterial infection. Interestingly, Nod1 is a detector of peptides and muropeptides containing the meso-2,6 ... [more ▼]

The mammalian proteins, Nod1 and Nod2, are able to recognize peptidoglycan motifs during bacterial infection. Interestingly, Nod1 is a detector of peptides and muropeptides containing the meso-2,6-diaminopimelic acid (m-A2pm), a non-proteinogenic amino acid found in Gram- bacteria. In this work, we describe a synthesis of peptidoglycan motifs entirely on solid support. Solid-Phase Peptide Synthesis (SPPS), Cross Metathesis (CM) and sugar chemistry are three methods to anchor respectively amino acids, m-A2pm and sugars derivatives on a resin as solid support. [less ▲]

[18F]UCB-H is a fluorine-18 radiolabelled PET imaging tracer with a high affinity for the synaptic vesicle protein 2A (SV2A). This protein, involved in vesicle trafficking and widely distributed in the ... [more ▼]

[18F]UCB-H is a fluorine-18 radiolabelled PET imaging tracer with a high affinity for the synaptic vesicle protein 2A (SV2A). This protein, involved in vesicle trafficking and widely distributed in the brain, represents the binding site and the primary mechanism of the antiepileptic drug levetiracetam. Levetiracetam has recently been suggested to reduce synaptic deficits in a mouse Alzheimer’s disease model and to improve cognition in patients with amnestic mild cognitive impairment, suggesting a possible role for this protein in synaptic integrity. The objective of this study was to investigate the cerebral distribution of [18F]UCB-H in healthy human volunteers. Dynamic PET imaging of the head of four healthy volunteers was performed over 100 minutes after injection of 170.4 ± 24.9 MBq of GMP produced [18F]UCB-H. The input function was acquired by arterial blood sampling during the dynamic PET acquisition. Blood data analysis showed a consistent tracer amount in whole blood and plasma indicating a very low degree of binding of the tracer to the red blood cells. Unchanged [18F]UCB-H fraction in plasma follows a bi-exponential behavioral decrease with a starting fraction of 92% of the injected amount of the tracer, measured at 3 min post injection. This fraction decreases to about 50% at 10 min post injection. The [18F]UCB-H PET data revealed a high and rapid uptake in the grey matter structures, matching the known ubiquitous distribution of SV2A in the brain. The kinetics of the tracer in the brain was characterized by an initial high uptake phase followed by rapid washout allowing the standard compartmental modeling (1-tissue compartment, 2-tissue compartment, and Logan graphical analysis). The three models gave consistent results. The two-tissue compartment model fitted the experimental data best and provided a total distribution volume of [18F]UCB-H in the brain greater than 7 mL/cm3 and a specific distribution volume around 3 mL/cm3. Our results indicate that [18F]UCB-H is a new radiotracer for brain SV2A proteins suitable for human studies. Further studies are warranted to assess SV2A modifications in neurological pathologies such as Alzheimer’s disease. [less ▲]

Purpose: Dynamic microPET imaging has advantages over traditional organ harvesting, but is pronetoquantificationerrorsinsmallvolumes.Hybridimaging,wheremicroPETactivitiesarecross- calibrated using post scan harvested organs, can improve quantification. Organ harvesting, dynamic imaging and hybrid imaging were applied to determine the human and mouse radiation dosimetry of 6-[18 F]fluoro-L-DOPA and 2-[18 F]fluoro-L-tyrosine and compared. Procedures: Two-hour dynamic microPET imaging was performed with both tracers in four separate mice for 18 F-FDOPA and three mice for 18 F-FTYR. Organ harvesting was performed at 2, 5, 10, 30, 60 and 120 min post tracer injection with n=5 at each time point for 18 F-FDOPA and n=3 at each time point for 18 F-FTYR. Human radiation dosimetry projected from animal data was calculated for the three different approaches for each tracer using OLINDA/EXM. S- factors for the MOBY phantom were used to calculate the animal dosimetry. Results: Correlations between dose estimates based on organ harvesting and imaging was improved from r=0.997 to r=0.999 for 18 F-FDOPA and from r=0.985 to r=0.996 (p<0.0001 for all) for 18 F-FTYR by using hybrid imaging. Conclusion: Hybrid imaging yields comparable results to traditional organ harvesting while partially overcoming the limitations of pure imaging. It is an advantageous technique in terms of number of animals needed and labour involved. [less ▲]

Multivariate classification is used in neuroimaging studies to infer brain activation or in medical applications to infer diagnosis. Their results are often assessed through either a binomial or a ... [more ▼]

Multivariate classification is used in neuroimaging studies to infer brain activation or in medical applications to infer diagnosis. Their results are often assessed through either a binomial or a permutation test. Here, we simulated classification results of generated random data to assess the influence of the cross-validation scheme on the significance of results. Distributions built from classification of random data with crossvalidation did not follow the binomial distribution. The binomial test is therefore not adapted. On the contrary, the permutation test was unaffected by the cross-validation scheme. The influence of the crossvalidation was further illustrated on real-data from a brain–computer interface experiment in patients with disorders of consciousness and from an fMRI study on patients with Parkinson disease. Three out of 16 patients with disorders of consciousness had significant accuracy on binomial testing, but only one showed significant accuracy using permutation testing. In the fMRI experiment, the mental imagery of gait could discriminate significantly between idiopathic Parkinson’s disease patients and healthy subjects according to the permutation test but not according to the binomial test. Hence, binomial testing could lead to biased estimation of significance and false positive or negative results. In our view, permutation testing is thus recommended for clinical application of classification with cross-validation. [less ▲]

in Clinical EEG and Neuroscience : Official Journal of the EEG and Clinical Neuroscience Society (ENCS) (2014)

Visual analysis of electroencephalography (EEG) background and reactivity during therapeutic hypothermia provides important outcome information, but is time-consuming and not always consistent between ... [more ▼]

Visual analysis of electroencephalography (EEG) background and reactivity during therapeutic hypothermia provides important outcome information, but is time-consuming and not always consistent between reviewers. Automated EEG analysis may help quantify the brain damage. Forty-six comatose patients in therapeutic hypothermia, after cardiac arrest, were included in the study. EEG background was quantified with burst-suppression ratio (BSR) and approximate entropy, both used to monitor anesthesia. Reactivity was detected through change in the power spectrum of signal before and after stimulation. Automatic results obtained almost perfect agreement (discontinuity) to substantial agreement (background reactivity) with a visual score from EEG-certified neurologists. Burst-suppression ratio was more suited to distinguish continuous EEG background from burst-suppression than approximate entropy in this specific population. Automatic EEG background and reactivity measures were significantly related to good and poor outcome. We conclude that quantitative EEG measurements can provide promising information regarding current state of the patient and clinical outcome, but further work is needed before routine application in a clinical setting. [less ▲]

It is well established that cognition shows daily fluctuations with changes in circadian phase and sleep pressure. The physiological impact of season changes, which is well characterized in animals ... [more ▼]

It is well established that cognition shows daily fluctuations with changes in circadian phase and sleep pressure. The physiological impact of season changes, which is well characterized in animals, remains largely unexplored in human. Here we investigated the impact of seasonal variation on human cognitive brain function. This cross-sectional study,conducted in Liège (Belgium),spanned from May 2010 to October 2011. Following 8h in-lab baseline night of sleep, 30 volunteers (age 20.9+1.5; 15F)spent 42h awake under constant routine conditions(<5lux, semi-recumbent position, no time-cues). After12h recovery night, they underwent15minfMRI recording while performing a working memory 3-back task (3b) and a letter detection 0-back task (0b). Thus, fMRI data were acquired when volunteers had been in isolation under controlled conditionsfor 63h. Executive brain responses were isolated by subtracting 0b activity from 3b responses (3b>0b).Analysis tested seasonal influence on executive brain responses at the random effects level, using a phasoranalysis across the year.Inferences were conducted at p<0.05, after correction for multiple comparisons over a priori small volume of interest. Significanteffects of season on executive responses were detected inmiddle frontal and frontopolarregions, insula, and thalamus, with a maximum response at the end of summer and a minimum response at the end of winter.These brain areas are key regions for executive control and alertness. These results constitute the first demonstration that seasonality directly impacts on human cognitive brain functions. [less ▲]

The synthesis of modified tripeptides (S)-Ala-[gamma]-(R)-Glu-X, where X = (R,S) or (R,R) diastereomers of [small alpha]-benzyl or [small alpha]-(4-azidobenzyl)lanthionine, was carried out. The chemical strategy involved the enantioselective alkylation of a 4-MeO-phenyloxazoline. The reductive opening of the alkylated oxazolines, followed by cyclization and oxidation, led to four PMB-protected sulfamidates. Subsequent PMB removal, Boc protection and regioselective opening with cysteine methyl ester led to protected lanthionines. These compounds were further converted in a one pot process to the corresponding protected tripeptides. After ester and Boc deprotection, the four tripeptides were evaluated as potential analogues of the natural tripeptide (S)-Ala-[gamma]-(R)-Glu-meso-A2pm. These compounds were evaluated for introduction, by means of the biosynthetic recycling pathway, into the peptidoglycan of Escherichia coli. A successful in vitro biosynthesis of UDP-MurNAc-tripeptides from the tripeptides containing [small alpha]-benzyl lanthionine was achieved using purified murein peptide ligase (Mpl). Bioincorporation into E. coli W7 did not occur under different tested conditions probably due to the bulky benzyl group at the C[small alpha] carbon of the C-terminal amino acid. [less ▲]

The three diastereoisomers-(R,R), (S,S) and meso-of lanthionine were synthesized in aqueous solution with high diastereoselectivity (>99%). The (S) and (R) enantiomers of two differently protected ... [more ▼]

The three diastereoisomers-(R,R), (S,S) and meso-of lanthionine were synthesized in aqueous solution with high diastereoselectivity (>99%). The (S) and (R) enantiomers of two differently protected sulfamidates were opened by nucleophilic attack of (R) or (S)-cysteine. Acidification and controlled heating liberated the free lanthionines. Using the same chemistry, an alpha-benzyl lanthionine was also prepared. The proposed method, which avoids the need of enrichment by recrystallization, opens the way to the labelling of these compounds with (35)S. Furthermore, in vivo bioincorporation into Escherichia coli W7 was studied. No incorporation of alpha-benzyl lanthionine was observed. In contrast, meso-lanthionine can effectively replace meso-diaminopimelic acid in vivo, while in the presence of (R,R)-lanthionine the initial increase of bacterial growth was followed by cell lysis. In the future, meso-[(35)S]lanthionine could be used to study the biosynthesis of peptidoglycan and its turnover in relation to cell growth and division. [less ▲]